Production of thiols and thioethers



Fatented Sept. 16, 1952 PRODUCTION OF THIOLS Ami 'rHioE'rHERs Graham H. Short, Bartlesville, kla., assignorto Phillips Petroleum Company, a corporation of Delaware No Drawing. Application August 28, 1947, Serial No. 771,157

This invention relates to an improved process for the manufacture of organic sulfur compounds. In one embodiment, this invention relates to the direct addition of a compound having the formula. RSI-Lin which R represents hydro'gen or an organic radical substantially inert under the reaction conditions used, to an ethylenic linkage in an organic compound, in the presence of. a novel catalyst to produce mercaptans and/or organic sulfides. A more specific embodiment involves the manufacture of useful mercaptans from olefins and hydrogen sulfide through-the agency of activated montmorillonite clayas a catalyst, and the invention will be described with particular reference to this embodiment;

An object of the invention is to effect catalytically the addition of (1) hydrogen sulfide or (2) mercaptans, to olefinic materials to produce (1) mercaptans and/or (2) sulfides.

The direct synthesis of organic sulfur compounds, especially merc'aptans and sulfides (thioethers), by the addition of hydrogen sulfide or mercaptans to olefinic materials, with or without the presence of a catalyst, has been reported by various investigators. However, the specificity of these reactions has not been of the order frequently required, due to the elevated temperatures employed for straight thermal reaction, and due to the consequent production of undesirable side reactions by virtue of the thermal instability of the desired product, and also due to the production of saturated hydrocarbons at high temperatures which seriously interfere with the yield of the desired organic sulfur compounds.

Catalytic processes with particular emphasis on the manufacture of low molecular weight mercaptans, have been advanced. Recommended solid contact catalysts have previously included metallic sulfides, fullers earth, silica gel, and charcoal. The activity of these catalysts leaves much to be desired, since temperatures of 400 to 500 F. are often necessary toeffect reaction at a practical rate. Adsorptive clays of the fullers earth type have been proposed as catalysts for this reaction. Such catalysts are in some cases suitable for the production of relatively low molecular weight mercaptans because of their pronounced depolymerizing activity toward the higher olefins. However, this property often re- 7 Claims. (Greta-s09) suits in aninefiicient process when high-boiling r 2 mercaptans are desired. In general, it may be stated that the natural adsorption catalysts thus far proposed for the olefin-hydrogen sulfide or the olefin-mercaptan reaction are deficient in activity, and especially in specificity, in the production of mercaptans and sulfides containing twelve or more carbon atoms per molecule.

The process of the present invention comprises the contacting of controlled proportions of an olefinic hydrocarbon, or an olefini c hydrocarbon mixture, such as a mixture of dodecylene and higher homologues, and hydrogen sulfide 'or an alkyl mercaptan or mercaptans with a solid contact catalyst which comprises activated montmorillonite clay. 'The process is particularly applicable to the manufacture of high-boiling mercaptans and/or thio'ethers by the direct addition of hydrogen sulfide and/or mercaptans to olefins containing eight or more carbon atoms per molecule. The improved process of this invention utilizes an adsorptive solid-contact catalyst of such specificity and activity that high-boiling olefins can be converted to the corresponding mercaptans and/or thioethers with a minimum of depolymerization and other undesirable side reactions; Other objects and advantages of the invention will become apparent to one skilled in the art from the accompanying descriptionand discussion. The process disclosed is of particular value in the manufacture of'high-boiling mercaptans which are exceptionally desirable modifiers in the manufacture of synthetic rubber of the Buna type, such as copolymers of diolefins with vinyl compounds such as styrene, acrylonitrile, esters of acrylic acid, etc. f a

It has now been found that the olefin-hydrogen sulfide reaction, and the olefin-mercaptan reaction, as applied to Ca and higher olefins to produce high-boiling mercaptans and/or thioerei is smooth y e e ted the Pr sen p an activated montmorillonite clay. This type of catalyst is described in an article by Davidson et al. at pages R-3l8 to -R-321 of National Petroleum News," issue of July 7, 1943.

The preferredcatalysts usedvin the process of this invention occur in nature-before activation-as montmorillonite, which is believed to have the ideal formula A12Si-1O1o(OH) 2nH2O, and an actual formula corresponding to MgQAlzOzSiOanHzO,

since' in nature the ideal formula is not realized due to substitutions. The natural montmorillonite clay has a crystalline rather than an amorphous or gel structure, as exemplified by silica gel. One apparently typical substitution in the formula of the product as found in nature is partial replacement of aluminum by magnesium. This montmorillonite mutation does not appear to be haphazard, but characteristically every sixth aluminum ion is apparently supplanted by a magnesium ion, and this replacement of a trivalent cation (aluminum) by a divalent cation (magnesium) is believed to give rise to a deficiency in positive charge. The crystal lattice of the ideal montmorillonite unit crystal cell is characterized by a layer configuration, and each layer is believed to consist offour sheets of oxygen, between the outer sheets of which in the tetrahedral position are located the silicon atoms; in the octahedral position are the aluminum atoms, and in the same oxygen sheets which form the boundaries of the octahedrals are the hydroxyl ions. The deficiency in positive charge caused in the neutral product by the replacement of the trivalent cation by the divalent cation causes the lattice to become negatively charged, and in order to neutralize this charge, various types of cations are adsorbed on the crystal protruding into the water of hydration space between the layers of montmorillonite. The cations, being exposed, are subject to mass action effects and are readily replaceable, thus giving rise to the phenomenon of base exchange which is a characteristic of the substituted montmorillonite. I 7 7 The raw montmorillonite clay 'is commonly classified as a non-swelling bentonite and is sometimes referred to as a su-bbentonite.

Modification f the raw montmorillonite to provide a suitable catalyst for the present invention is effected by-activation. The most common form of activation is by means of an acid, and in treating a magnesium substituted montmorillonite in the raw form for use as a catalyst by acid activation, impurities are removed with-attendant increase in effective catalytic surface, and also exchangeable ions are replaced by hydrogen; i. e., the surface cations originally present in a magnesium substituted montmorillonite lattice are replaced by hydrogen ions as a result of the activation. Thus, the activated material may be termed a magnesium substituted hydrogen montmorillonite. A further effect of the acid treatment in activating the montmorillonite clay may well be to dissolve a disproportionate amount of alumina, thus increasing the percentage of magnesia. A sample of the activated montmorillonite clay is characterized by the following analysis:

The catalyst is of the solid contact type and is preferably used in this invention in the form of pellets rangin in size from four to twenty mesh. Ten grams of this particular material in the form of 4-8 mesh pellets were washed with 50 cc. of distilled water, whereupon the wash water' acquired a pH of 3.0. It is obvious that the above analysis of the particular percentages of magnesia, alumina, silica, and water will vary within reasonable limits, depending on various factors, such as the source of the clay, the extent and character of the acid treatment, etc.

This invention is not limited to the addition of hydrogen sulfide and mercaptans to the higher olefins, but also extends to the use of lower molecular weight olefins; although the latter are not full equivalents in the operations described. A definite gradation in reactivity exists between qthe lower and higher members of the aliphatic olefin series, thus requiring somewhat different conditions for effective conversion to the correspondin mercaptans and/or thioethers.

In a specific preferred embodiment of the invention, a Cl2-C14 fraction, derived from the catalytic polymerization of C3 and C4 olefins, in admixture with the desired molal proportion of hydrogen sulfide is contacted with the catalyst under the following conditions; pressures ranging from about to 1,500 pounds gage; temperatures from about atmospheric to about 400 F.; catalyst comprising a magnesium substituted'hydrogen montmorillonite; flow-rate of one to ten liq uid volumes per volume of catalyst per hour. Under the aforesaid conditions, the principal reaction occurring is apparently addition of H28 to the olefinic linkages so that the combined sulfur is found in mercaptans corresponding substantially in boiling range to those expected from the composition of the olefin feed. The total effluent from the reaction zon is treated byconventional means for recovery of hydrogen sulfide and the unreacted hydrocarbon is fractionated out of the product. This latter operation is preferably accomplished under diminished pressure.

The hydrocarbon-hydrogen sulfide or hydrocarbon-mercaptain feed mixture may be passed continuously through a stationary bed of the solid granular contact catalyst or otherwise contacted with the solid catalyst, and the catalyst efiluent may be either continuously or intermittently fractionated to separate unreacted' olefin and hydrogen sulfide and/or mercaptan from the product. In producing mercaptans, ordinarily an excess of hydrogen sulfide is present in the feed which may be returned to the catalyst along with fresh olefin. Operation may be either batchwise or continuous, with the latter usually preferred. A plurality of catalyst cases may be provided in order to maintain uninterrupted operation during catalyst replacement or regenerationprocedure; In-

stead of feeding hydrogen sulfide predissolved in the olefin charge, other means of introduction to the reaction zone may be employed. For example, hydrogen sulfide may be added at one or more points directly into the catalyst chamber in order tomaintain a predetermined concentration at various points within the catalyst space. Temperatur control within the catalyst space may to about-eight mesh.

to the high degree ofspecificitytowardpromo,- tion of the mercaptan reaction exhiblted by. the catalyst of this. invention, only a moderate excess of hydrogen sulfide is required. Satisfactory reaction mixtures may contain olefin-hydrogen sulfide in ratios of between about 1:1 and .a range of about four to about twenty mesh, but,

if'de'sired, may be used as a fine powder in suspension in the reacting stream. The preferred mesh range for the catalyst is from about'jour The temperature within the catalystibed, or

the reaction temperature, is chosen to conform with the catalyst activity, the feed composition,

the operating pressure, and'the, reaction time in order to secure mosteificierit conversion of the olefin to mercaptan or thioether Suitable temperatures over the range of preferred operating conditions are usually within the range .of about 100 F. to about 400 withasomewhatnan I rower range. of about 1505: to about "[250? F.

However, higher temperatures are" permissible.

It is one of the features of this inventionthat the catalyst employed has thebeneficiaI e'fiect of reduced depolymerization or. cracking ofhigh molecular weight olefins, permits the use of higher temperatures for'the reactions, and result's'in higher yields of high molecular weight mercaptans and/or sulfides at the usual temperatures of reaction; f I Since the mercaptan andthioether syntheses described hereinbefore are exothermi me'ans for dissipating any excess heat and preventing excessive temperature'increases are ordinarily. provided. Such means may include cooling the catalyst bedb'y internal or external heat exchange apparatus, or, more conveniently, by reducing the amount of preheat suppliedto the feed'aha'd of the catalyst, or use of 'an inert diluent. Excessive temperatures tend to favor formation of hydrocarbon decomposition products 7 Catalyst life in the present process is ordinarily very long, since the relatively low temperatures and the mixed phase operation both tend to prevent the accumulation'of tarry poisonsfan'd carbonaceous deposits. Thus, several hundred volumes of high-boiling mercaptan and/or thioether may often be produced per volume of catalyst before any significant change in activity is evident. V V v Operating pressures are chosen in With reaction requirements. For example;- the desired mercaptan-forming reaction isapparent- 1y promoted to some extent by pressure which may be effective by virtue of the increased hydrogen sulfide concentration at the active'centers of the contact catalyst. Relatively high pressures also tend to prevent the formation of low' molecular weight mercaptans. The .preferred pressures are usually in the range of about 100 to 3,000 pounds gage; however, operation most conveniently and economically carried out between about 500 to about 1,000 pounds gage pressure.

When temperature and pressure conditions are selected to conform with catalyst. activity and desired extent of conversion, rather high" flow rates offreactants may be employed. Withthe preferred catalysts of this invention, flow rates accordance .for optimum results.

the feed mixture according to this invention are preferably straight or branched-chain alkyl mercarbon atoms.

as high; as ten, liquid volumes of .fieed per hour per volume of catalyst may be employed.

; As will be appreciatedby one skilled in the art,

other process modifications may be employed. A reaction mixture may be passed in a closed continuous cycle through a fixed catalyst bed,

with reactants, being continuouslyadded near the entrance of the bed and with a portion of the circulating mixture being withdrawn from the system and with recoveryof a desired mercaptan product, or fraction, from such portion. The catalyst, in finely-divided form, may be suspended in the reaction mixture, which is then passed directly through the reaction zone or which may be reacted in a continuously circulating stream. In any of such'modiflcations, the reactionmixture may be in asingle phase, or in mixed vapor-liquid phase, with or without vapqrization of a liquid phase during reaction to aid in temperature control. a 1 l Y Q The feed stocks for the process of-manufacture of the desired highebo iling mercaptans and/or thioethers .maybe derived from any suitable 1 source, -suc h as .catalytic polymerization units.

In some cases it;is desi rable to utilize a feed rich commercial tri-isobutylne or a close-cut fractionofheavy polymer produced in the catalytic polymerization of C2-C8 olefins may be employed.

The latter feed source is especially desirable, and

550 F.=at 760 mm. may besatisfactorily utilized in the present process for synthesis .of mercaptans and/or sulfides having from eleven to sixteen carbon atoms per alkyl radical :within the moleu e- The hydrogen sulfide may be derived from any convenient source, and is particularly abundant as a by-product from petroleum refining processes and from natural gasoline treating plants. Pure hydrogen sulfide, while often desirable, is not essential to the successful operation of this in- ,vention; although it is preferred to have the concentration of, impurities, such as carbon-dioxide,

below about five per centof the hydrogensulfide, The mercaptans used in captans; These' mercaptans may contain .as many as twenty or more carbon atoms; preferably they fall in the range of one to sixteen V The improved efficiency of the catalyst in accordance with this invention extends both to the low molecular Weightmercaptan-olefin' reactions as well as to the high molecuthe invention may be practiced by first forming the'mercaptan by the use of the catalyst. de-

scribed. herein; whereupon, either with or without isolation of the mercaptan producedfrom the feed mixture, further olefin, or olefinszmay be added and the reaction continued to produce a relatively high yield of thioether or thioethers.

'When the latter system is used, the conditions may be controlled to produce maximum utilizati o'n of thehydrogen sulfide and the 'mercapta'n adiated 'brmercaptans. with attendarit mnnmizauon or hydrogen sulfide andm'ercaptans in the eifluent. The process of 1 recovering the high-boiling 'n'iercap'tans' and/or thioethers from the-catalyst -eiiluent' comprises a stabilization or-distillation operation for the rec'overy-ofurireacted hydrogen "sulfide or mercaptans, as the case-may be; a stripping operation for the removal of 'unreact'e'd olefin and/or hydrocarbon'impurities, and-finally "a fractional distillation of the-mercaptan or thioether product. The stripping and distillation operations maybe carried *out as diminishedpressure'operations as ordinarily carried out with vacuum pumps 01' with steam. Other methods of separating mercaptan or thioether from unreacted 'olefins' and other material, especially solvent extraction; may be employed, if desired.

' The catalyst used in the reactionaccording'to this invention permits the use of higher temperatures for the reaction and results in higher yields of higher molecular weight sulfur reactionproducts at the usual temperatures of reactionfThe catalyst is'also more effective than previouscatalysts, including various natural and synthetic silica-alumina and silica-zirconia catalysts.

In order further to illustrate thespecific'uses and advantages of the present invention, the following exemplary-operations will be described. However, since these-and numerous other-process modifications will be obvious in the'light-of the foregoing disclosure, no undue limitations are intended.

1 Example! Pellete'd magnesium substituted hydrogen montmorillonite, asdescribed above, 1 was ground 'to'atwelve to twenty-mesh-size and used to-pack a;10O-cc. catalyst case.

'Hydrogen sulfide was dissolved in an-olefin charge stock with a boiling point at 760 mm.'Hg in the range 420 F. to 520 F., and'comprising approximately 98 per cent of Cn'to'Cm olefins until a mol ratio of hydrogen-sulfide to olefin of 1.511 was obtained. This composition'was passed overfthe twelve to twenty-mesh catalyst at'an average reaction temperature of'about 230"F. at "a rate of one liquid volumeper volume of catalyst per hour and a pressure of 1,000 p. s. i.-g. The effluent product was treated to remove unreactecl hydrogen sulfideand olefin, which could then be recycled 'to'the reactionzone. The'yield of mercapta'n product amounted to eighty per cent of the converted olefin, upon"'a weight basis.

Example II 7 six hundred and fifty gallons of four to-eightmesh pellets'of magnesium substituted hydrogen montmorillonite, as described above, were placed in a catalystchamber for hydrogen 'sulfide' olefin -synthesis. The olefin feedwas a 400F. to 460 F.iraction of heavy polymer from a'catalytic polymerization unit treatinga mixture of C1 olefins. The composition of this fraction consists primarily of C14 olefins.

The feed for the mercaptan reaction'was prepared by blending hydrogen sulfide to the olefin fraction in'a'm'ol ratio of 1.5:1. The feed blend was charged to the'catalyst case undera pressure of ,000 p.'s. i. g. Areaction temperature'o'f 200 toi220 F. was maintained at a chargefratepf two liquidvolumes pervolumeiof catalyst per hour. "The'efiluent'raw product was washed to :remove Hes and then fractionally distilled under reduced pressure to :remove 'unreacted "olefin.

'The"final' productas'sa'yed ninety percent. mer- "'ca'ptan, -boiling1between12401 'andlrabout 300 :F. --'at' 5mm. Hg pressure.

Under-these conditions, only a minor quantity 0107 and lighter mercantans was obtained and substantially no alkyl thioethers. The yield of 'mercaptan amountedito about one hundred'per cent ofthe' converted ole- 'fl fi'upon a weight basis.

' Example III A test 'was run using reaction conditionsall respects comparable to-Example II, except that -asilica-alumina"catalyst, as described in application-Serial No; 493,463, wasused in lieu of'the activated 'montmorillonite. The yield of C14 mercaptanamounted to about seventy per cent by weight based on converted feed-stock. The

increase in effectiveness 'of the process of 'EX- ample 11 over the previousprocess, represented by Example III, is'indicated by the higher yield of the desired C14 mercaptanand the lower yield of the C1 mercaptan;

' What is'claimed is:

'1. Aprocess"of makingthiols and thio'ethers 'which' comprisescontacting at a temperature between-' and 400 F; an olefin hydrocarbon having at least 8 carbon-atoms per molecule,'with a molar excess of a compound having the formula RSI-I; where 'R is selected from the group consisting of hydrogen and alkyl radicals, substantially non-reactive under the reaction conditions, in the presence of an acid activated montmorillonite catalyst; comprising a crystalline montmorillonite; which in its naturally occurringstate has "one-sixth of the'aluminum replaced "by magnesium, in which the ratio of alumina "to magnesia is-about 3 to 1, the amount-of alumina 'being about 18'per cent ona dry basis, the residue other than-alumina and magnesiabeing'essentially silica.

'2. The process in accordance 'withclaim -1,-in which'the olefin fraction has-a boiling range from about 100-to 500 Rand is composed'principall of C13 andCm olefins.

molecule, with a compound having the formula "RSH, where R is-selected from the group consisting of hydrogenand alkyl radicals, substantially non-reactive under the reaction conditions, in the presence of an acid activated montmorillonite catalyst, comprising a crystalline montmorillonite, which in its naturally occurringstate has one-sixth of the aluminum replaced 1 by magnesium'and on a'dry basis contains about'18 00' cipally of C13 and C16 olefins.

6.:The process in accordancewith claim 4 in whichthe olefin feed has a boiling range. from "mula' RSI-I, where Risselected from the group consisting or hydrogen "and *alkyl radicals sub- 9 stantially non-reactive under the reaction conditions, in the presence of an acid activated montmorillonite which has substantially the weight analysis: 4.9% magnesia, 14.4% alumina, 21.9% water, and the remainder is silica.

GRAHAM H. SHORT.

REFERENCE S CITED The following references are of record in the file of this patent:

Number 10 UNITED STATES PATENTS Name Date Reuter et a1 Dec. '7, 1937 Rummelsburg Apr. 10, 1945 Badertscher et a1. "1 Oct. 16, 1945 Schulze Jan. 8, 1946 Schulze Jan. 8,1946 Gary et a1 Sept. 21, 1948 OTHER REFERENCES Duffy et 211., Ind. and Eng. Chem., January 1934, pp. 91-93.

Jones et a1., Jour. Am. Chem. $00., vol. 60, Y October 1938, pp. 2452-55. 

